The oxo process is the commercial application of the hydroformylation reaction for making higher alcohols and aldehydes from olefins. In the cobalt oxo process, an olefin reacts with carbon monoxide and hydrogen (i.e., syn gas) at elevated temperatures in the presence of a cobalt carbonyl catalyst to produce a hydroformylation reaction product which is subsequently decobalted or demetalled to produce a crude product mixture of aldehydes, alcohols, acetals, formates, unreacted olefins and secondary products. Subsequent hydrogenation steps provide the desired finished alcohol products commonly referred to as oxo alcohols (i.e., alcohols produced by an oxonation reaction).
One aspect of the overall cobalt oxo process involves the preparation of the active cobalt catalyst species which is hydrido cobalt carbonyl (HCo(CO).sub.4). Commercial oxo processes employ a preforming step in which this active cobalt catalyst species is prepared from a cobalt salt, e.g., cobalt formate, using a noble metal preforming catalyst. This preforming step is disclosed, for example, in U.S. Pat. No. 4,404,119, which issued Sep. 13, 1983, to Lagace et al. and in U.S. Pat. No. 4,255,279, which issued Mar. 10, 1981, to Spohn et al.
The present inventors have developed an improvement in the process for preparing oxo alcohols by the cobalt catalyzed hydroformylation of C.sub.2 to C.sub.17 linear or branched monoolefins with subsequent hydrogenation of the hydroformylation reaction product which has been disclosed in co-pending U.S. patent application, Ser. No 08/122,859, filed on Sep. 16, 1993. In this co-pending application the aqueous solutions of cobalt salts have been converted to active hydrido cobalt carbonyl species in a preformer reactor, the preformer containing (i) preformer metal catalyst of Group IB or VIII of the Periodic Table or (ii) a preformer non-metallic catalyst selected from the group consisting of activated carbon, ion exchange resins, silica alumina and zeolites. The preformer catalyst was reactivated according to co-pending U.S. patent application, Ser. No. 08/122,859 by treating it at a temperature of about 120.degree. C. to 170.degree. C. and at a pressure of about 13.88 MPa (2,000 psig) to 31.10 MPa (4,500 psig) and preferably about 20.77 MPa (3,000 psig), with water or with a mixture of water and hydrogen or a mixture of water and syn gas for a period of about 2 to 50 hours, whereby the conversion of the cobalt salts to hydrido cobalt carbonyl is improved when such salts are contacted with the treated preformer catalyst.
The use of activated carbon as a preformer catalyst, as suggested in U.S. patent application, Ser. No. 08/122,859, fails to produce the catalytic activity necessary for converting the cobalt salt to hydrido cobalt carbonyl in sufficient yields when the organic employed in the preformer is a hydrocarbon, an alcohol containing eight or more carbon atoms, a hydroformylation product (i.e., aldehydes, paraffins and unconverted olefins) or a hydrogenation product (i.e., paraffins and unconverted olefins). It would be highly desirable to be able to use activated carbon or other carbonaceous materials as the preforming catalyst since this material is substantially less expensive than conventional preformer metal catalysts of Group IB or VIII of the Periodic Table, i.e., palladium.
The present inventors have developed a unique process which increases the catalytic activity of carbonaceous materials such that they can be successfully used as preforming catalysts in the conversion of cobalt salt to hydrido cobalt carbonyl in the presence of any organic stream.
The process of the present invention utilizes an aqueous cobalt salt solution in the presence of light alcohols and syn gas at elevated pressures and temperatures to activate the carbonaceous material by depositing cobalt, e.g., hydrido cobalt carbonyl, on the surface thereof. The deposited cobalt then acts as a preforming initiator which substantially increases the catalytic activity of the carbonaceous material.
The present inventors have discovered that using carbonaceous catalysts during preforming of cobalt salts in the presence of light alcohols promotes more rapid formation and deposition of hydrido cobalt carbonyl on the surface of the catalyst than when other types of organics are used. The use of light alcohols with the cobalt salts also prevents deposition of cobalt as cobalt metal or cobalt salts on the carbon surface.
On the other hand, treating carbonaceous preforming catalysts with an aqueous cobalt salt solution in the presence of other organics (e.g., heavy alcohols or aldehydes) or as a mixture of light alcohols and other organics as suggested in U.S. patent application, Ser. No. 08/122,859 will not produce catalytic activity equivalent to that of the present invention.